Since an electric double layer capacitor has a large scale of an F (farad) class and is excellent also in charge-and-discharge cycle characteristics, it is used as a backup power supply of electrical machinery and apparatus, an in-vehicle battery, etc.
The electric double layer capacitor is equipped with a pair of polarized electrodes, a separator arranged between the polarized electrodes, and an electrolyte. The polarized electrode separated with the separator is constituted, respectively so that it may act as an anode plate and the cathode. Activated carbon having pores is usually used as a material of the polarized electrode of such an electric double layer capacitor. Electrolytic ion in an electrolyte is adsorbed in the pore of the activated carbon to form an electric double layer, thereby constituting an anode plate and a cathode of a capacitor, respectively.
As the process for producing the above polarized electrode, a process is disclosed in Japanese Unexamined Patent Application, First Publication No. H07-105316. In this process, a mixture consisting of powdery activated carbon, a fluorine containing polymer resin and a liquefied lubricant (solvent for lubrication) is shaped into a sheet, thereafter the liquefied lubricant is removed by heating, extracting, etc. It should be noted that the document fails to disclose how the liquefied lubricant is removed to what level, specifically.
By the way, the activated carbon which is used in an electric double layer capacitor has originally a character being excellent in the adsorption capability of chemical substances, and this adsorption capability is derived from the existence of the pore of the activated carbon mentioned above. Therefore, when the liquefied lubricant is not sufficiently removed but remained in the pore, formation of the electric double layer by adsorption set of electrolytic ion is prevented, and there is a problem that the internal resistance of the electric double layer capacitor increases.